1. Field of the Invention
The present invention relates to an integrated optical head, and more particularly to an integrated optical head which is suitably used in an optical information recording and reproducing apparatus such as an optical disk memory.
2. Related Background Art
In the optical information recording and reproducing apparatus such as optical disk memory or opto-magnetic disk memory, an optical head is used to irradiate light for recording and reproducing information to and from a record medium and detect a light from the record medium. A conventional optical head uses a bulk type head having various optical parts including lenses and splitters arranged in alignment.
Since such bulk type optical head has a limitation on size reduction, it cannot fully meet a size reduction requirement. The bulk type optical head needs assembling and adjustment of optical parts in the manufacture thereof, and it is hard to prepare the heads of uniform performance.
In order to enhance the compactness and reliability, the optically integrated optical head has been recently proposed. For example, U.S. application Ser. No. 825,695 (Continuation of U.S. Ser. No. 482,894), FIG. 6 and page 13, lines 5-18, and U.S. application Ser. No. 651,780, FIG. 1B and page 2, line 16 to page 3, line 15 show and describe the optical information recording apparatus which use the integrated optical heads.
FIG. 1 shows a perspective view of a conventional integrated optical head. Numeral 2 denotes a substrate on which an optical wave guide 1 is formed. A grating coupler 30 having a light focusing function is formed on the surface of the optical wave guide. Numeral 3 denotes a semiconductor laser which serves as a light source. The laser is coupled to an end surface of the optical wave guide 1.
In this optical head, a laser beam from the semiconductor laser 3 is coupled to a diverging guided wave 31 in the optical wave guide 1 by the end surface coupling. When the diverging guided wave reaches the focusing grating coupler 30, it is coupled by the coupler to a focusing light 32 which propagates in a space. An exit focusing light in focused to a predetermined point S in the space as shown in FIG. 1. By arranging an information record medium at the point S, the light beam is spot-irradiated thereto.
While not shown, a reflected light from the information record medium is also coupled to the guided wave in the optical wave guide 1 by a focusing grating coupler (not shown) and detected by a photodetector (not shown).
In the conventional integrated optical head, very high precision is required to prepare the focusing grating coupler which can produce a light spot close to a diffraction limit, and hence it is difficult to attain a high precision optical head because of manufacturing tolerance.
Further, even if the focusing grating coupler is manufactured with high precision, it is very difficult to attain ideal use condition thereof. Since a large aberration is created due to deviations of an incident angle of incident light to the grating coupler, a wavelength of the incident light and an incident point of the incident light, it is very difficult to attain high light focusing performance.